New ab Initio Potential Energy Surfaces for the Renner-Teller Coupled 𝟏^𝟏𝐴^′ and 1^𝟏𝐴^′′ States of CH₂

Figure 4

The bending potential energy curves for the four singlet states (1¹𝐴^′, 1¹𝐴^′′, 2¹𝐴^′′, and 3¹𝐴^′) of CH₂ calculated at the icMRCI(6e, 7o)+Q/AVQZ level. (The 2¹𝐴^′state, which lies between the 1¹𝐴^′ and 3¹𝐴^′ state, is not shown.) 𝑅_CH1 = 𝑅_CH2 = 2.01 bohrs. The zero energy is taken at the CH₂ (1¹𝐴^′) minimum.